1. Field of the Invention
This invention relates to a monitor, and more particularly to an image control method and apparatus that is capable of controlling a contrast and a color temperature in a digital monitor.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) is one of a plat panel display device that display a picture by controlling a transmitted amount of a light beam to correspond to image signals. This LCD has advantages of a light weight, a thin thickness and a low power consumption. Owing to this, the LCD has been applied to display devices for an office automation equipment and a notebook computer as well as a monitor for a personal computer. The monitor is classified into an analog monitor and a digital monitor depending on a shape of input signals applied to the monitor from a graphic card. Such a monitor is required to control a brightness, a contrast and a color temperature in accordance with a picture display quality or as needed.
Referring to FIG. 1, an analog input signal 2 applied to an analog monitor is shown. The analog input signal 2 has an amplitude xcex94Vpp that is a difference between its maximum value Vph and its minimum value Vpl. The minimum value Vpl of this analog input signal 2 has a voltage difference from a zero level V0 by a direct current offset value xcex94Vpl_0. The zero level V0 of the analog input signal 2 is displayed into a most dark black when a liquid crystal panel of the analog monitor is a normally white type, whereas it is displayed into a most bright white when a liquid crystal panel of analog monitor is a normally black type.
In the case of an analog monitor, the brightness is controlled by adjusting the direct current offset xcex94Vpl_0 of the analog input signal 2. The contrast is controlled by adjusting the amplitude xcex94Vpp of the analog input signal 2. To this end, the analog monitor includes an amplifier 4 and an analog to digital converter (ADC) 6 connected, in series, to an input line 3 as shown in FIG. 2. The amplifier 4 amplifies the analog input signal 2 inputted via the input line 3 by its gain value and applies the amplified signal to the ADC 6. The ADC 6 converts an analog signal inputted from the amplifier 4 into a digital signal and applies the digital signal to a scaler 8. The scaler 8 converts a resolution of the digital signal from the ADC to be adaptive for a resolution of the liquid crystal panel. If a gain value of the amplifier 4 is controlled, then an amplitude xcex94Vpp of the analog input signal 2 in FIG. 1 is controlled to control the contrast to that extent. Also, if a direct current bias of the amplifier 4 is controlled, then the direct current offset value xcex94Vpl_0 of the analog input signal 2 in FIG. 1 is controlled.
The color temperature or each of red, green and blue colors can be controlled into a desired value by installing the amplifiers 4 at each input line coupled with red, green and blue analog input signals 2 as shown in FIG. 3 and controlling gain values and direct bias voltages of the amplifiers 4. In FIG. 3, Gx represents a gain value per channel, and Ox does a direct current offset value per channel.
Referring now to FIG. 4, there is shown a digital monitor that includes a transmission minimized differential signal (TDMS) receiver 16 connected to a graphic card 10 in series. The graphic card 10 is provided with a TDMS transmitter 14 connected between a graphic controller 12 and the TDMS receiver 16. The graphic controller 12 converts a graphic signal to be adaptive for a resolution of the liquid crystal panel and applies it to the TDMS transmitter 14. The TDMS transmitter 14 encodes a digital graphic signal inputted from the graphic controller 12 into a TDMS signal that is a serial-type graphic signal. The TDMS receiver 16 decodes the TDMS signal from the TDMS transmitter 14 into a parallel-type signal. Since a graphic signal applied from the graphic card 10 is encoded into a digital type to apply the same to the digital monitor as described above, it is impossible to control an amplitude xcex94Vpp or a direct current offset xcex94Vplxe2x80x940 like the analog input signal 2. Accordingly, the digital monitor is able to control the brightness by a brightness control of the back light only, but is difficult to correct the brightness, the contrast and the color temperature by controlling the input signal. In particular, the digital monitor has a problem in that correction of the contrast and the color temperature is substantially impossible.
Accordingly, it is an object of the present invention to provide an image control method and apparatus for a digital monitor that is capable of controlling a contrast and a color temperature in the digital monitor.
In order to achieve these and other objects of the invention, an image control method for a digital monitor according to one aspect of the present invention includes the steps of producing an offset control signal; adding a digital input signal to the offset control signal; and limiting an added value of the digital input signal and the offset control signal within a desired reference value.
An image control method for a digital monitor according to another aspect of the present invention includes the steps of producing an contrast control signal; multiplying a digital input signal by the contrast control signal; and limiting a multiplied value of the digital input signal and the contrast control signal within a desired reference value.
An image control method for a digital monitor according to still another aspect of the present invention includes the steps of producing an offset control signal and a contrast control signal; adding a digital input signal to the offset control signal; multiplying the digital input signal by the contrast control signal; limiting an added value of the digital input signal and the offset control signal within a desired reference value; and limiting a multiplied value of the digital input signal and the contrast control signal within a desired reference value.
An image control apparatus for a digital monitor according to still another aspect of the present invention includes control means for producing an offset control signal; a digital adder for adding a digital input signal to the offset control signal; and added value control means for limiting an added value of the digital input signal and the offset control signal within a desired reference value applied from the control means.
An image control apparatus for a digital monitor according to still another aspect of the present invention includes control means for producing a contrast control signal; a digital multiplier for multiplying a digital input signal by the offset control signal; and multiplied value control means for limiting a multiplied value of the digital input signal and the contrast control signal within a desired reference value applied from the control means.
An image control apparatus for a digital monitor according to still another aspect of the present invention includes control means for producing an offset control signal and a contrast control signal; a digital adder for adding a digital input signal to the offset control signal; a digital multiplier for multiplying the digital input signal by the offset control signal; added value control means for limiting an added value of the digital input signal and the offset control signal within a desired reference value applied from the control means; and multiplied value control means for limiting a multiplied value of the digital input signal and the contrast control signal within a desired reference value applied from the control means.